High-purity semi-insulating single-crystal silicon carbide wafer and crystal

ABSTRACT

The present disclosure provides high-purity semi-insulating single-crystal silicon carbide wafer and crystal which include one polytype single crystal. The semi-insulating single-crystal silicon carbide wafer has silicon vacancy inside, wherein the silicon-vacancy concentration is greater than 5E11 cm{circumflex over ( )}-3.

CROSS REFERENCE TO RELATED DISCLOSURE

This application claims the priority benefit of Taiwan PatentApplication Number 109120678, filed on Jun. 18, 2020, the fulldisclosure of which are incorporated herein by reference.

BACKGROUND Technical Field

The application relates to the technical field of semi-insulatingsingle-crystal silicon wafer and crystal, particularly to high puritysemi-insulating single-crystal silicon carbide wafer and crystal withhigh silicon-vacancy concentration.

Related Art

Semiconductor materials have gone through three stages of development.The first generation is about basic functional materials of silicon(Si), germanium (Ge), etc.; the second generation is about compoundsemiconductor materials composed of two or more elements, whereingallium arsenide (GaAs), indium phosphide (InP), etc. arerepresentative; the third generation is about compound semiconductormaterials such as gallium nitride (GaN) and silicon carbide (SiC). Thesemiconductor materials of the third generation are materials with wideenergy band gaps, which have the advantages of high frequency, highvoltage resistivity, and high-temperature resistivity. The semiconductormaterials of the third generation have good electrical conductivity andheat dissipation to reduce energy consumption. The volume of elementscomprised the semiconductor materials of the third generation isrelatively small, thereby suitable for power semiconductor applications.However, controlling the production conditions of silicon carbide isdifficult, which makes the mass production of silicon carbide wafersdifficult. Thereby, the development of terminal wafers and applicationsis affected directly.

Physical vapor transport (PVT) is currently the mainstream method forthe commercial mass production of silicon carbide crystal. Generally,the process of growing silicon carbide crystals by the physical vaportransmission method is: preparing a seed and placing the seed in acrucible includes a growth chamber, a holder, and a material sourcecontainer, wherein the holder is disposed above the growth chamber andused for fixing the seed, the holder is disposed at the relatively coldend of the thermal field device that provides the temperature gradient,and the material source container is disposed below the growth chamberto contain the material source; placing the carbide material in thematerial source container; sublimating the carbide material from solidto gas molecules; and transporting and depositing the sublimated gasmolecules on the seed to grow the crystal.

In order to manufacture a high-resistivity silicon carbide wafer, thehigh-purity raw materials and deep-level dopants such as vanadium dopingare mainly used in the prior art. Further, the reactive gas andshallow-level conduction elements are provided in the annealing processor neutron bombardment during the crystal growth process to make thewafer have high resistivity characteristic. However, when the size ofthe crystal is increased, the uniform resistivity and yield oflarge-sized crystals are not sufficiently provided by the prior artmethod. Therefore, the process cost is increased. In addition, due tothe factors of crystal growth equipment, crystals with larger sizes (forexample, larger than 4 inches) are more difficult to produce, and theyield rate is not easy to improve.

SUMMARY

Given the defect of the above-mentioned prior art, the presentapplication provides semi-insulating single-crystal silicon carbidewafer and crystal which are large-size, high-resistivity, andless-defect, particularly to high-purity semi-insulating single-crystalsilicon carbide wafer and crystal with high silicon-vacancyconcentration.

A semi-insulating single-crystal silicon carbide wafer according to anembodiment of the present application comprise one polytypesingle-crystal, wherein the semi-insulating single-crystal siliconcarbide wafer has silicon vacancy inside, and the silicon-vacancyconcentration is at least greater than 5E11 cm{circumflex over ( )}-3.

The high resistivity characteristic of the large-size high-puritysemi-insulating single-crystal silicon carbide wafer or crystaldisclosed in the present application is dominated by the concentrationof crystal intrinsic defects (i.e. silicon vacancy) generated in thecrystal growth process. Therefore, the additional annealing process orneutron bombardment process is unneeded to implemented to the wafer. Inthe prior art, the silicon-vacancy concentration of silicon carbide isabout 2E11 cm{circumflex over ( )}-3 to 3E11 cm{circumflex over ( )}-3.The silicon-vacancy concentration of the silicon carbide wafer orsilicon carbide crystal disclosed in the present application is at leastgreater than 5E11 cm{circumflex over ( )}-3.

Other advantages of the present application will be explained in moredetail with the following descriptions and figures.

It should be understood, however, that this summary may not contain allaspects and embodiments of the present invention, that this summary isnot meant to be limiting or restrictive in any manner, and that theinvention as disclosed herein will be understood by one of ordinaryskill in the art to encompass obvious improvements and modificationsthereto.

BRIEF DESCRIPTION OF THE DRAWINGS

The figures described herein are used to provide a further understandingof the application and constitute a part of the application. Theexemplary embodiments and descriptions of the application are used toillustrate the application and do not limit the application, in which:

FIG. 1 is a schematic diagram of the growth system for growinghigh-purity semi-insulating single-crystal silicon carbide crystalaccording to the present application;

FIG. 2 is a measurement result of the resistivity of the high-puritysemi-insulating single-crystal silicon carbide crystal according to thefirst embodiment of the present application;

FIG. 3 is a schematic diagram of the micro-pipe density of thehigh-purity semi-insulating single-crystal silicon carbide crystalaccording to the first embodiment of the present application;

FIG. 4 is an electron paramagnetic resonance spectrum of the high-puritysemi-insulating single-crystal silicon carbide crystal according to thefirst embodiment of the present application;

FIG. 5 is a measurement result of the resistivity of the high-puritysemi-insulating single-crystal silicon carbide crystal according to thesecond embodiment of the present application;

FIG. 6 is a schematic diagram of the micro-pipe density of thehigh-purity semi-insulating single-crystal silicon carbide crystalaccording to the second embodiment of the present application;

FIG. 7 is an electron paramagnetic resonance spectrum of the high-puritysemi-insulating single-crystal silicon carbide crystal according to thesecond embodiment of the present application;

FIG. 8 is a schematic diagram of the silicon-vacancy concentration ofthe silicon carbide wafer according to the second embodiment of thepresent application;

FIG. 9 is a photoluminescence spectrum of a silicon carbide waferaccording to the second embodiment of the present application;

FIG. 10 is a photoluminescence spectrum of a silicon carbide waferaccording to the second embodiment of the present application;

FIG. 11 is a schematic diagram of the PL/TO ratio according to the firstembodiment of the present application;

FIG. 12 is a schematic diagram of the micro-pipe density of thehigh-purity semi-insulating single-crystal silicon carbide waferaccording to the third embodiment of the present application; and

FIG. 13 is a schematic diagram of the micro-pipe density of thehigh-purity semi-insulating single-crystal silicon carbide waferaccording to the fourth embodiment of the present application.

DETAILED DESCRIPTION OF THE EMBODIMENTS

In order to make the objectives, technical solutions, and advantages ofthe present application clearer, the technical solutions of theapplication will be described clearly and completely in conjunction withspecific embodiments and the figures of the application. Obviously, thedescribed embodiments are only a part of the embodiments of theapplication, rather than all the embodiments. Based on the embodimentsin the application, all other embodiments obtained by a person ofordinary skill in the art without creative work fall within theprotection scope of this disclosure.

The following description is of the best-contemplated mode of carryingout the invention. This description is made for the purpose ofillustrating the general principles of the invention and should not betaken in a limiting sense. The scope of the invention is best determinedby reference to the appended claims.

Certain terms are used throughout the description and following claimsto refer to particular components. As one skilled in the art willappreciate, manufacturers may refer to a component by different names.This document does not intend to distinguish between components thatdiffer in name but function. “Substantial/substantially” means, withinan acceptable error range, the person skilled in the art may solve thetechnical problem in a certain error range to achieve the basictechnical effect.

Moreover, the terms “include”, “contain”, and any variation thereof areintended to cover a non-exclusive inclusion. Therefore, a process,method, object, or device that comprises a series of elements not onlyinclude these elements, but also comprises other elements not specifiedexpressly, or may include inherent elements of the process, method,object, or device. If no more limitations are made, an element limitedby “include a/an . . . ” does not exclude other same elements existingin the process, the method, the article, or the device which comprisesthe element.

In the following embodiment, the same reference numerals are used torefer to the same or similar elements throughout the invention.

The present application discloses a high-purity semi-insulatingsingle-crystal silicon carbide crystal with large-size,high-resistivity, and low-defect, which is grown in a high-puritysingle-crystal system by physical vapor transport (PVT). By controllingthe Si/C ratio and particle size distribution of the high-purity crystalgrowth raw material, and the crystal growth temperature and time duringthe crystal growth process, the system becomes a carbon-rich (C-rich)environment. In a state where shallow-level conductive elements arescarce, the intrinsic defect of silicon vacancy may be generated in thecrystal and the silicon-vacancy concentration may be controlled. Theintrinsic defect is used to increase the resistivity of the crystal inorder to make the wafer semi-insulate. In addition, the possibility ofintroducing impurities into the crystal is eliminated during the crystalgrowth process due to the high-purity raw material. Therefore, thepresent application discloses a high-purity semi-insulatingsingle-crystal silicon carbide bulk material with a micro-pipe defectless than 3 cm{circumflex over ( )}-2.

“Large size” mentioned here refers to a high-purity semi-insulatingsingle-crystal silicon carbide wafer with a diameter of at least 4inches, or 4 inches to 6 inches, and a thickness of at least 350 μm.“High purity” refers to the purity of the raw material used for growncrystal is higher than 99.99%. “High resistivity” refers to theresistivity is greater than 1E7 ohm-cm or at least 1E7 ohm-cm at roomtemperature. In addition, the crystal refers to a silicon carbidecrystal manufactured by a silicon carbide growth system in theembodiments of the specification, and the finished product after cuttingthe silicon carbide crystal is generally called a wafer.

The high resistivity characteristics of the high-purity semi-insulatingsingle-crystal silicon carbide crystal or silicon wafer of the presentapplication are controlled by the concentration of intrinsic defect(silicon vacancy) in the crystal or wafer. The silicon vacancy isgenerated during the crystal growth process. An additional annealingprocess or neutron bombardment process is unnecessary therebysimplifying the manufacturing process.

Refer to FIG. 1, which is a schematic diagram of the growth system forgrowing high-purity semi-insulating single-crystal silicon carbidecrystal according to the present application. As shown in the figure,the growth system comprises a crucible 2, a thermal insulation material3, and a heater 7. The crucible 2 is used to contain a seed 1 whichgrows through a material source 6. The thermal insulation material 3 isdisposed on the outside of the crucible 2. The thermal insulationmaterial 3 shown in the figure covers the outside of the crucible 2, butthe thermal insulation material 3 does not have to substantially coverthe outside of the crucible 2, as long as the temperature may bemaintained. Therefore, the figure is only exemplary. The heater 7 isused to provide a heat source. The number of the heater 7 shown in thefigure is multiple, but the number of the heater 7 may also be providedin one depending on the system configuration. The number of the heater 7in the figure is only for the purposes of exemplary and does not limitthe real number of heater 7. A high-frequency heater or a resistivityheater may be used as the heater 7. In a more specific embodiment, aheating coil or heating resistivity wire (net) may be used as the heater7.

A holder 4 is disposed above the inside of the crucible 2, and theholder 4 is used to fix the seed 1. The material source 6 may bedisposed below the crucible 2, and the space between the seed 1 and thematerial source 6 may be used as a growth area 5 for silicon carbidecrystal. The area where the seed 1 is placed may be defined as the seedarea, and the area where the material source 6 is placed may be definedas the material source area. Therefore, the empty crucible 2 has a seedarea, a material source area, and a growth area inside. In anon-limiting embodiment, the crucible 2 may be a graphite crucible, andthe thermal insulation material 3 may be a graphite blanket or a porousthermal insulation carbon material.

In the embodiment, the seed may be silicon carbide. The seed used in thepresent application may be a single-crystal wafer with a thickness of350 μm or more and a diameter of 4 inches to 6 inches or more to grow asingle-crystal with the corresponding size or more. The single-crystalwafer may be silicon carbide. The material source area in the cruciblemay be silicon carbide. The material source may be powdery, granular, ormassive and have a purity of more than 99.99%. The crystalline phase ofthe material source may be a or (3, and the ratio of silicon/carbon maybe 0.95 to 1.05.

By controlling the temperature distribution, the atmosphere flow, andthe sublimation process of the material source in the crucible 2 withthe structure of the crucible 2, the structure of the thermal-material3, and the heater 7, the sublimated gas molecules are transported anddeposited on the seed 1 (wafer) to generate silicon carbide crystal. Inan embodiment of the growth process, the temperature difference betweenthe bottom of the crucible to the seed area is controlled in the rangeof 10° C. to 300° C., the flow rate of argon gas is controlled in therange of 100 sccm to 1000 sccm, the pressure is controlled in the rangeof 1 torr to 200 torrs, and the temperature range of the seed duringcrystallization is controlled between 2000° C. and 2270° C. Controllingthe purity and type of the material source, and the temperature rangeand time of growth are the most important. After the conductive elementsinside the system are consumed, the electrical performance of thecrystal may be majorly dominated by the intrinsic defect generatedinside the crystal.

The high-purity semi-insulating single-crystal silicon carbide crystalformed by the growth system of the above embodiment is grown bydepositing a vapor material containing Si and C on the surface of theseed. The high-purity semi-insulating single-crystal silicon carbidecrystal comprises one polytype single-crystal. The high-puritysemi-insulating single-crystal silicon carbide crystal has siliconvacancy inside, wherein the silicon-vacancy concentration is at leastgreater than 5E11 cm{circumflex over ( )}-3 and less than 5E13cm{circumflex over ( )}-3. In the prior art, the concentration ofsilicon vacancy in silicon carbide wafer is about 2E11 cm{circumflexover ( )}-3 to 3E11 cm{circumflex over ( )}-3 generally.

In one embodiment, the high-purity semi-insulating single-crystalsilicon carbide crystal formed by the growth system according to theabove embodiment has a diameter greater than or equal to 90 mm.

In one embodiment, the diameter of the high-purity semi-insulatingsingle-crystal silicon carbide crystal formed by the growth systemaccording to the above embodiment is less than or equal to 200 mm.

In one embodiment, the high-purity semi-insulating single-crystalsilicon carbide crystal formed by the growth system according to theabove embodiment has a resistivity greater than 1E7 ohm-cm.

In one embodiment, the high-purity semi-insulating single-crystalsilicon carbide crystal formed by the growth system according to theabove embodiment has a micro-pipe density of less than 3 per squarecentimeter.

In one embodiment, the high-purity semi-insulating single-crystalsilicon carbide crystal formed by the growth system according to theabove embodiment has a micro-pipe density of less than 2 per squarecentimeter.

In one embodiment, the high-purity semi-insulating single-crystalsilicon carbide crystal formed by the growth system according to theabove embodiment has a micro-pipe density of less than 1 per squarecentimeter.

In one embodiment, the high-purity semi-insulating single-crystalsilicon carbide crystal formed by the growth system according to theabove embodiment has a micro-pipe density of less than 0.4 per squarecentimeter.

In one embodiment, the high-purity semi-insulating single-crystalsilicon carbide crystal formed by the growth system according to theabove embodiment has a micro-pipe density of less than 0.1 per squarecentimeter.

In one embodiment, the high-purity semi-insulating single-crystalsilicon carbide crystal formed by the growth system according to theabove embodiment comprises one polytype single-crystal selected from 3C,4H, 6H, and 15R polymorphs of silicon carbide, wherein the 4H polymorphis the most preferred currently. The wafer may be selected from 3C, 4H,6H, and 15R polymorphs of silicon carbide, wherein the 4H polymorph isthe most preferred currently. The wafer obtained is oriented along anaxis, such as a positive axis orientation, or a variety of off-axisorientations. For example (but not limited to), the wafer is selectedfrom 4°, 3.5°, and 2°.

In one embodiment, the thickness of the high-purity semi-insulatingsingle-crystal silicon carbide crystal formed by the growth systemaccording to the above embodiment is at least 8 mm.

In one embodiment, the thickness of the high-purity semi-insulatingsingle-crystal silicon carbide crystal formed by the growth systemaccording to the above embodiment is 8 mm to 30 mm.

The following embodiment illustrates the specific manufacturing processof the high-purity semi-insulating single-crystal silicon carbidecrystal disclosed in the present application. Through physical vaportransport (PVT), using high-purity growth materials and components, andadjusting process window and time, the manufacturing process is not onlyeffectively inhibiting impurities and conductive elements from enteringthe crystal during the crystal growth process but improving the qualityof the crystal. By thermal field optimization and process control, theoverall crystal growth surface is flatter, and the intrinsic defectconcentration of the crystal is increased. Thereby, the resistivity of1E7 ohm-cm of the silicon carbide crystal with 4 to 6 inches isachieved.

The first embodiment illustrates growing a 6-inch single-crystal siliconcarbide crystal by using the growth system of FIG. 1. The material usedin the present embodiment is high-purity silicon carbide powder with apurity of 99.99% or more. The average particle size is 5 mm to 20 mm.The initial silicon/carbon ratio is 1. After the crystal growing, thesilicon/carbon ratio of the remaining material drops to 0.85.

The 4H-SiC single-crystal is manufactured by the PVT method with theabove-mentioned silicon carbide source. The growth process is performedin a graphite crucible in a high-temperature vacuum induction furnace.The growth temperature of the seed is about 2100° C. Ar is used as thecarrier gas for the system. The pressure during crystal growth of thesystem is about 5 torr, and the growth time is 150 hours. A siliconcarbide single crystal wafer of about 500 μm is used as a seed.

First, perform an air extraction process, and fix the 4H-SiC seed with aholder. Then, extract air to remove air and other impurities in thecrucible system. After extracting the air, perform a heating process.During the heating process, add the inert gas Ar as auxiliary gas, anduse the heating coil to heat the entire system. Heat to about 2100° C.and continually grow for up to 150 hours. Through the process conditionsof the first embodiment, a 6-inch single-crystal silicon carbide boulewith a convex interface shape may be produced, and the crystal growthrate may achieve 100-250 μm/hr.

The resistivity, micro-pipe density, impurity elements, or siliconvacancy of the crystal after growing may be measured. The crystal aftergrowing is sliced and polished to obtain a wafer. The wafer may bemeasured for resistivity without annealing. An area with a diameter of140 mm at the center of the 6-inch wafer is measured, the resistivityvalues are all greater than 1E7 ohm-cm, as shown in FIG. 2.

Analyze the 6-inch wafer with X-ray topography. As the result, thenumber of micro-pipes is 10. Furthermore, the overall density of 6-inchmicro-pipes is the number of micro-pipes/6 inch wafer area, which is10/(7.5*7.5*3.1416)=10/176.75=0.056. That is, the micro-pipe density inthis embodiment is less than 0.1 per square centimeter, as shown in FIG.3.

Analyze the impurity elements of the 6-inch wafer with Glow DischargeMass Spectrometer (GDMS) and Secondary Ion Mass Spectroscopy (SIMS), theresults of the following table may be obtained. Wherein, the N elementis measured by SIMS, and other elements are measured by GDMS. Two unitsof ppm and ion concentration are provided. The content of conductiveimpurity elements in the crystal is less than 5E15 cm{circumflex over( )}-3.

Crystal number Example 1 element GDMS (ppm/cm{circumflex over ( )}-3) NSIMS: 4.30E+15 B 0.02 (3.76E+15) Al 0.04 (2.87E+15) P <0.05 (<3.14E+15)Ti <0.01 (<4.04E+14) V <0.01 (<3.38E+14) Fe <0.1 (<3.46E+15) Ni <0.05(<1.67E+15)

Analyze the 6-inch wafer with the electron paramagnetic resonance (EPR).The spectroscopy shows that the main defect in the crystal is siliconvacancy. As shown in FIG. 4, the results of the optical inspection areused to show the silicon-vacancy concentration. The silicon-vacancyconcentration is from 5.22E11 cm{circumflex over ( )}-3 to 1.02E12cm{circumflex over ( )}-3.

The second embodiment illustrates growing a 4-inch single-crystalsilicon carbide boule by using the growth system of FIG. 1. The materialused in the present embodiment is high-purity silicon carbide powderwith a purity of 99.99% or more. The average particle size is 100 mm to30 mm. The initial silicon/carbon ratio is 1. After the crystal growing,the silicon/carbon ratio of the remaining material drops to 0.87.

The 4H-SiC single-crystal is manufactured by the PVT method with theabove-mentioned silicon carbide source. The growth process is performedin a graphite crucible in a high-temperature vacuum induction furnace.The growth temperature of the seed is about 2180° C. Ar is used as thecarrier gas for the system. The pressure during crystal growth of thesystem is about 5 torr, and the growth time is 200 hours. A siliconcarbide single crystal wafer of about 500 μm is used as a seed.

First, perform an air extraction process, and fix the 4H-SiC seed with aholder. Then, extract air to remove air and other impurities in thecrucible system. After extracting the air, perform a heating process.During the heating process, add the inert gas Ar as auxiliary gas, anduse the heating coil to heat the entire system. Heat to about 2100° C.and continually grow for up to 150 hours. Through the process conditionsof the first embodiment, a 6-inch single-crystal silicon carbide boulewith a convex interface shape may be produced, and the crystal growthrate may achieve 100-250 μm/hr.

The resistivity, micro-pipe density, impurity elements, or siliconvacancy of the crystal after growing may be measured. The crystal aftergrowing is sliced and polished to obtain a wafer. The wafer may bemeasured for resistivity without annealing. An area with a diameter of140 mm at the center of the 6-inch wafer is measured, the resistivityvalues are all greater than 1E7 ohm-cm, as shown in FIG. 5.

Analyze the 6-inch wafer with X-ray topography. As the result, thenumber of micro-pipes is 1. Furthermore, the overall density of 4-inchmicro-pipes is the number of micro-pipes/4 inch wafer area, which is1/(5*5*3.1416)=1/78.54=0.012. That is, the micro-pipe density in thisembodiment is less than 0.02 per square centimeter, as shown in FIG. 6.

Analyze the impurity elements of the 6-inch wafer with Glow DischargeMass Spectrometer (GDMS) and Secondary Ion Mass Spectroscopy (SIMS), theresults of the following table may be obtained. Wherein, the N elementis measured by SIMS, and other elements are measured by GDMS. Two unitsof ppm and ion concentration are provided. The content of conductiveimpurity elements in the crystal is less than 5E15 cm{circumflex over( )}-3.

Crystal number Example 2 element GDMS (ppm/cm{circumflex over ( )}-3) NSIMS: 1.90E+15 B 0.04 (6.93E+15) Al 0.03 (2.10E+15) P <0.05 (<3.14E+15)Ti <0.01 (<4.04E+14) V <0.01 (<3.38E+14) Fe <0.1 (<3.46E+15) Ni <0.05(<1.67E+15)

Analyze the 4-inch wafer with the electron paramagnetic resonance (EPR).The spectroscopy shows that the main defect in the crystal is siliconvacancy. As shown in FIG. 7, the results of the optical inspection areused to show the silicon-vacancy concentration. The silicon-vacancyconcentration is 7.07E12 cm{circumflex over ( )}-3.

Cut the crystal of the second embodiment, and analyze thesilicon-vacancy concentration of the slices at different positions, asshown in FIG. 8. Taking the growth system of FIG. 1 as an example, atotal of 20 slices are cut, and the 20 slices respectively correspondingto the serial number on the horizontal axis of FIG. 8. Wherein theserial number of the slice closest to the seed is 1. From the seed tothe growth surface, the silicon-vacancy concentrations respectively are1.9E12 cm{circumflex over ( )}-3, 7E12 cm{circumflex over ( )}-3, 5.9E12cm{circumflex over ( )}-3, and 3.3 E12 cm{circumflex over ( )}-3,respectively.

The high-purity semi-insulating single-crystal silicon carbide waferaccording to the above embodiment comprises one polytype single-crystal.The high-purity semi-insulating single-crystal silicon carbide wafer hassilicon vacancy inside, wherein the silicon-vacancy concentration is atleast greater than 5E11 cm{circumflex over ( )}-3, less than 5E13cm{circumflex over ( )}-3.

In one embodiment, the high-purity semi-insulating single-crystalsilicon carbide wafer formed according to the above embodiment has adiameter greater than or equal to 90 mm.

In one embodiment, the diameter of the high-purity semi-insulatingsingle-crystal silicon carbide wafer formed according to the aboveembodiment is less than or equal to 200 mm.

In one embodiment, the high-purity semi-insulating single-crystalsilicon carbide wafer formed according to the above embodiment has aresistivity greater than 1E7 ohm-cm.

In one embodiment, the high-purity semi-insulating single-crystalsilicon carbide wafer formed according to the above embodiment has amicro-pipe density of less than 3 per square centimeter.

In one embodiment, the high-purity semi-insulating single-crystalsilicon carbide wafer formed according to the above embodiment has amicro-pipe density of less than 2 per square centimeter.

In one embodiment, the high-purity semi-insulating single-crystalsilicon carbide wafer formed according to the above embodiment has amicro-pipe density of less than 1 per square centimeter.

In one embodiment, the high-purity semi-insulating single-crystalsilicon carbide wafer formed according to the above embodiment has amicro-pipe density of less than 0.4 per square centimeter.

In one embodiment, the high-purity semi-insulating single-crystalsilicon carbide wafer formed according to the above embodiment has amicro-pipe density of less than 0.1 per square centimeter.

In one embodiment, the high-purity semi-insulating single-crystalsilicon carbide wafer formed according to the above embodiment comprisesone polytype single-crystal selected from 3C, 4H, 6H, and 15R polymorphsof silicon carbide, wherein the 4H polymorph is the most preferredcurrently. The wafer may be selected from 3C, 4H, 6H, and 15R polymorphsof silicon carbide, wherein the 4H polymorph is the most preferredcurrently. The wafer obtained is oriented along an axis, such as apositive axis orientation, or a variety of off-axis orientations. Forexample (but not limited to), the wafer is selected from 4°, 3.5°, and2°.

The wafer according to the present application is suitable forhigh-frequency power devices, high-power devices, high-temperaturedevices, optoelectronic devices, and deposition of group III nitrides.

The wafer according to the present application is suitable as asingle-photon light source, that is, an integrated circuit substrate ofa quantum computer.

Refer to FIG. 9, the electron paramagnetic resonance (EPR) spectrum ofthe second embodiment is shown. The sample was cut into a size of 5.5cm×7 mm and irradiated with a microwave of 9.70396×1E9 Hz. In thespectrum, the silicon carbide wafer produces a zero point at 3600.70343Gat a temperature of 300K. After calculation by the formula hυ=gμ_(B)B(h: Planck's constant, υ: frequency; g: g factor; μ_(B): Bohr magneton;B: magnetic field), the g factor of the No. 11 wafer of Example 2 is2.00343. It means that the silicon vacancy is contained in siliconcarbide (the signal of silicon vacancy is g=2.0032±0.0004).

Refer to FIG. 10, which is the photoluminescence spectrum of the waferof the second embodiment. Some Raman signals are not sensitive to theconcentration of doping and the concentration of vacancy, for example,lateral-optical mode. For laser excitation of 785 nm, it is the LO modeat the 851 nm wavelength and the 4H-SiC TO mode at the 838 nmwavelength. In FIG. 9, the ratio of the photoluminescence to the Ramansignal at LO mode (ratio (PL/LO)) of the No. 19 wafer of the secondembodiment is 5.1. Therefore, the silicon-vacancy density of the secondembodiment is about 5.1±0.7=7.29 (×1E12 cm{circumflex over ( )}-3). Infact, the intensity and wavenumber of the peak of the LO mode aregreatly affected by the concentration of doping, and predicting thevacancy density of SiC through the ratio (PL/LO) is difficult. In orderto measure SiC with different resistivity, the photoluminescence signalof TO mode is used to measure the silicon-vacancy concentration becauseof its stability in different wafers and the same measurement area asphotoluminescence. In FIG. 9, the ratio of the photoluminescence to theRaman signal at the TO mode (ratio (PL/TO)) of the second embodiment is4.50. As a result, the silicon-vacancy density in 4H-SiC may becalculated by the following formula: density ofV_Si=PL/TO×7.29÷4.47=PL/TO×1.63. The PL/TO ratio is the peak ofcorresponding excitation light divided by the peak of the Ramanscattering at TO mode in the excitation spectrum (near 840 nm).Therefore, the silicon-vacancy density per unit lattice generatingsilicon-vacancy electroluminescence may be calculated (1PL/TO→1.630*10{circumflex over ( )}12/cm{circumflex over ( )}3).

The first embodiment was tested in the same method, and the maximumaverage vacancy density in the series was 3.26×1E12 cm{circumflex over( )}-3.

FIG. 11 is a schematic diagram of the PL/TO ratio of the firstembodiment. Taking the first embodiment as an example, nine measurementpoints are selected. The PL/TO ratio is shown in the figure, and thePL/TO ratio, silicon-vacancy concentration, and resistivity values ofthe nine measurement points (A, B, C, D, E, F, G, H, and I) are asfollows:

measurement PL/TO silicon-vacancy resistivity values point ratioconcentration (cm{circumflex over ( )}-3) (ohm-cm) A 0.45 7.34E+11 1E11B 0.43 7.01E+11 1E9  C 0.5 8.15E+11 1E11 D 0.32 5.22E+11 1E10 E 0.46.52E+11 1E11 F 0.64 1.04E+12 1E11 G 0.64 1.04E+12 1E11 H 0.65 1.06E+121E11 I 0.49 7.99E+11 1E10

FIG. 12 is a schematic diagram of the third embodiment of theapplication, and the diameter thereof is 60 mm. FIG. 13 is a schematicdiagram of the fourth embodiment of the application, and the diameterthereof is 120 mm. FIGS. 12 and 13 show the micro-pipe density (MPD). Inthe figure, the silicon carbide wafer is divided into multiple squares,and the numbers in the squares refer to the number of micro-pipes. Thenumber of micro-pipes in the third embodiment is 60. Dividing by thearea of the wafer, the micro-pipe density may be obtained as2.1/cm{circumflex over ( )}2. The number of micro-pipes in the fourthembodiment is 56. Dividing by the area of the wafer, the micro-pipedensity may be obtained as 0.5/cm{circumflex over ( )}2.

In the high-purity crystal growth system of the present application, bycontrolling the Si/C ratio and particle size distribution of thehigh-purity crystal growth raw material, and the crystal growthtemperature and time during the crystal growth process, the systembecomes a carbon-rich (C-rich) environment. In a state whereshallow-level conductive elements are scarce, the intrinsic defect ofsilicon vacancy may be generated in the crystal and the silicon-vacancyconcentration may be controlled. The intrinsic defect is used toincrease the resistivity of the crystal in order to make the wafer besemi-insulated.

A person of ordinary skill in the art will understand current and futuremanufacturing processes, method and step from the content disclosed insome embodiments of the present disclosure, as long as the current orfuture manufacturing processes, method, and step performs substantiallythe same functions or obtain substantially the same results as thepresent disclosure. Therefore, the scope of the present disclosureincludes the above-mentioned manufacturing process, method, and steps.

The above descriptions are only examples of this application and are notintended to limit this application. This disclosure may have variousmodifications and changes for a person of ordinary skill in the art. Anymodification, equivalent replacement, improvement, etc. made within thespirit and principle of this application shall be included in the scopeof the claims of this disclosure.

What is claimed is:
 1. A high-purity semi-insulating single-crystalsilicon carbide wafer, comprising one polytype single-crystal, whereinthe high-purity semi-insulating single-crystal silicon carbide wafer hassilicon vacancy inside, and a silicon-vacancy concentration is greaterthan 5E11 cm{circumflex over ( )}-3.
 2. The high-purity semi-insulatingsingle-crystal silicon carbide wafer according to claim 1, wherein thesilicon-vacancy concentration is less than 5E13 cm{circumflex over( )}-3.
 3. The high-purity semi-insulating single-crystal siliconcarbide wafer according to claim 1, wherein a resistivity of thehigh-purity semi-insulating single-crystal silicon carbide wafer isgreater than 1E7 ohm-cm.
 4. The high-purity semi-insulatingsingle-crystal silicon carbide wafer according to claim 1, wherein amicro-pipe density of the high-purity semi-insulating single-crystalsilicon carbide wafer is less than 3 per square centimeter.
 5. Thehigh-purity semi-insulating single-crystal silicon carbide waferaccording to claim 4, wherein a micro-pipe density of the high-puritysemi-insulating single-crystal silicon carbide wafer is less than 2 persquare centimeter.
 6. The high-purity semi-insulating single-crystalsilicon carbide wafer according to claim 5, wherein a micro-pipe densityof the high-purity semi-insulating single-crystal silicon carbide waferis less than 1 per square centimeter.
 7. The high-purity semi-insulatingsingle-crystal silicon carbide wafer according to claim 6, wherein amicro-pipe density of the high-purity semi-insulating single-crystalsilicon carbide wafer is less than 0.4 per square centimeter.
 8. Thehigh-purity semi-insulating single-crystal silicon carbide waferaccording to claim 7, wherein a micro-pipe density of the high-puritysemi-insulating single-crystal silicon carbide wafer is less than 0.1per square centimeter.
 9. The high-purity semi-insulating single-crystalsilicon carbide wafer according to claim 1, wherein the one polytypesingle-crystal is selected from 3C, 4H, 6H, and 15R polymorphs ofsilicon carbide.
 10. The high-purity semi-insulating single-crystalsilicon carbide wafer according to claim 1, wherein a diameter of thehigh-purity semi-insulating single-crystal silicon carbide wafer isgreater than or equal to 90 mm.
 11. The high-purity semi-insulatingsingle-crystal silicon carbide wafer according to claim 1, wherein adiameter of the high-purity semi-insulating single-crystal siliconcarbide wafer is less than or equal to 200 mm.
 12. The high-puritysemi-insulating single-crystal silicon carbide wafer according to claim1, wherein the high-purity semi-insulating single-crystal siliconcarbide wafer has a positive axis orientation.
 13. The high-puritysemi-insulating single-crystal silicon carbide wafer according to claim1, wherein the high-purity semi-insulating single-crystal siliconcarbide wafer has an off-axis orientation.
 14. The high-puritysemi-insulating single-crystal silicon carbide wafer according to claim13, wherein the off-axis orientation is selected from 4°, 3.5°, and 2°.15. A high-purity semi-insulating single-crystal silicon carbidecrystal, which is grown by depositing a vapor containing silicon andcarbon on the growth surface of a seed, comprising one polytypesingle-crystal, wherein the high-purity semi-insulating single-crystalsilicon carbide crystal has silicon vacancy inside, and asilicon-vacancy concentration is greater than 5E11 cm{circumflex over( )}-3.
 16. The high-purity semi-insulating single-crystal siliconcarbide crystal according to claim 15, wherein the silicon-vacancyconcentration is less than 5E13 cm{circumflex over ( )}-3.